直接Z型LaNiO3/Mn0.2Cd0.8S异质结催化剂光解水产氢性能及机理探究

以LaNiO_3纳米颗粒为基质,在水热法制备CdS的过程中引入Mn~(2+)离子,原位合成直接Z型LaNiO_3/Mn_(0.2)Cd_(0.8)S异质结光催化剂。分别采用场发射扫描电镜、X射线衍射、X射线光电子能谱、紫外可见漫反射光谱、氮气吸附-脱附测试以及电化学测试等分析方法对制备的催化剂进行表征。在光解水产氢测试中,LaNiO_3/Mn_(0.2)Cd_(0.8)S异质结光催化剂在5 h的H_2产量达到1 190.3μmol,相较于CdS和Mn_(0.2)Cd_(0.8)S,其H_2产量分别提高了 25倍和10倍。荧光和电化学实验证实,Mn~(2+)的引入能够有效地促进光生载流子的分离,同时LaNiO_3/Mn_(0.2)Cd_(0.8)S之间异质结的构筑能有效地促进光生载流子在界面间的迁移、分离,从而促进其光解水产氢效率和稳定性的提高。结合一系列表征和活性测试结果提出直接Z型光解水反应机理,很好地阐述了其光解水产氢活性和稳定性的增强。     

碳自掺杂石墨相氮化碳纳米片的制备及其在可见光照射下的光解水产氢性能

石墨相氮化碳(g?C3N4)由于具有对可见光吸收范围较窄和光生载流子分离效率低等缺陷,其光解水产氢活性较差。我们采用简单的一步热共聚法,以尿素和2,4,6?三氨基嘧啶(TAPD)混合物为前驱物,制备碳自掺杂纳米片(CNNS?x,x mg代表掺入TAPD的质量)。X射线衍射(XRD)、元素分析(EA)和X射线光电子能谱(XPS)等测试结果表明,来自TAPD的嘧啶环成功引入g?C3N4共轭体系中,使所得的CNNS?x具有较窄的带隙,较快的光生载流子迁移速率,从而提高其对可见光的吸收效率和光生载流子的分离效率。得益于此,CNNS?x在可见光照射下表现出较好的光解水产氢活性。特别是CNNS?30具有最佳光解水性能,其产氢速率可达57.6μmol·h-1,是g?C3N4纳米片(CNNS)的4倍。     

Cu/MoS2的熔盐电解法制备及其在碱性条件下析氢反应性能的提高

通过熔盐电解法并掺杂过渡金属Cu制备2种不同纳米结构的Cu/MoS_2。采用涂敷法制备工作电极,通过X射线衍射(XRD)、透射电子显微镜(TEM)、能量散射X射线谱(EDS)、扫描电子显微镜(SEM)、选区电子衍射(SAED)以及各种电化学手段验证了其结构和性能。结果表明,纳米片状Cu/MoS_2在碱性溶液(1 mol·L~(-1)KOH)中表现出优异的析氢催化性能:在电流密度为10 mA·cm~(-2)时过电位为199.6 mV,Tafel斜率为59 mV·dec~(-1),双电层电容为26.1 mF·cm~(-2),等效电荷转移电阻为12.4Ω,具有较为良好的电化学耐久性和稳定性。     

泡沫镍负载Fe2O3@Ni3S2纳米线网状结构电极的制备及其电催化析氧性能

通过两步水热法制备泡沫镍(NF)负载Fe_2O_3纳米粒子@Ni_3S_2纳米线网状结构电极(Fe_2O_3@Ni_3S_2/NF)。运用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、N_2吸附-脱附测试等方法对电极材料的物相和微观结构特征等进行了表征。水热条件下原位表面化学刻蚀生成的Ni_3S_2纳米线与三维多孔NF基体间拥有强结合力和低界面电阻,Fe_2O_3粒子均匀分布在纳米线的表面。在1 mol·L~(-1)的KOH溶液中,运用线性扫描伏安测试(LSV)、计时电位法、电化学交流阻抗测试(EIS)等对电极的电催化析氧(OER)性能进行了测试。结果表明:在100 mA·cm~(-2)的超高电流密度下,Fe_2O_3@Ni_3S_2/NF电极的OER过电势仅为223 mV,比Ni_3S_2/NF材料的过电势降低了285 mV;经过10 h计时电位测试,性能保持率高达80%。     

CompassR Yields Highly Organic-Solvent-Tolerant Enzymes through Recombination of Compatible Substitutions

The CompassR (computer-assisted recombination) rule enables, among beneficial substitutions, the identification of those that can be recombined in directed evolution. Herein, a recombination strategy is systematically investigated to minimize experimental efforts and maximize possible improvements. In total, 15 beneficial substitutions from Bacillus subtilis lipase A (BSLA), which improves resistance to the organic cosolvent 1,4-dioxane (DOX), were studied to compare two recombination strategies, the two-gene recombination process (2GenReP) and the in silico guided recombination process (InSiReP), employing CompassR. Remarkably, both strategies yielded a highly DOX-resistant variant, M4 (I12R/Y49R/E65H/N98R/K122E/L124K), with up to 14.6-fold improvement after screening of about 270 clones. M4 has a remarkably enhanced resistance in 60 % (v/v) acetone (6.0-fold), 30 % (v/v) ethanol (2.1-fold), and 60 % (v/v) methanol (2.4-fold) compared with wild-type BSLA. Molecular dynamics simulations revealed that attracting water molecules by charged surface substitutions is the main driver for increasing the DOX resistance of BSLA M4. Both strategies and obtained molecular knowledge can likely be used to improve the properties of other enzymes with a similar α/β-hydrolase fold.     

The Roles of Composition and Mesostructure of Cobalt-Based Spinel Catalysts in Oxygen Evolution Reactions

By using the crystalline precursor decomposition approach and direct co-precipitation the composition and mesostructure of cobalt-based spinels can be controlled. A systematic substitution of cobalt with redox-active iron and redox-inactive magnesium and aluminum in a cobalt spinel with anisotropic particle morphology with a preferred 111 surface termination is presented, resulting in a substitution series including Co₃O₄, MgCo₂O₄, Co₂FeO₄, Co₂AlO₄ and CoFe₂O₄. The role of redox pairs in the spinels is investigated in chemical water oxidation by using ceric ammonium nitrate (CAN test), electrochemical oxygen evolution reaction (OER) and H₂O₂ decomposition. Studying the effect of dominant surface termination, isotropic Co₃O₄ and CoFe₂O₄ catalysts with more or less spherical particles are compared to their anisotropic analogues. For CAN-test and OER, Co³⁺ plays the major role for high activity. In H₂O₂ decomposition, Co²⁺ reveals itself to be of major importance. Redox active cations in the structure enhance the catalytic activity in all reactions. A benefit of a predominant 111 surface termination depends on the cobalt oxidation state in the as-prepared catalysts and the investigated reaction.     

Ruthenium nanoclusters anchored on cobalt phosphide hollow microspheres by green phosphating process for full water splitting in acidic electrolyte

Transition metal phosphide(TMP) based electrocatalysts possessing special crystal and electronic structures attract broad attention in the field of electrocatalysis.Immense effort is made to optimize TMP catalysts aiming to satisfy the electrochemical catalysis performance.In this work,an environmentally friendly in situ green phosphating strategy and spatial limiting effect of the RuCo precursor is employed to fabricate the ruthenium nanoclusters anchored on cobalt phosphide hollow microspheres(Ru NCs/Co₂P HMs).The obtained Ru NCs/Co₂P HMs electrocatalysts exhibit high hydrogen evolution reaction(HER) activity at wide pH ranges,which require an overpotential of 77 mV to achieve the current density of 10 mA/cm² in 0.5 mol/L H₂SO₄ and 118 mV in 1.0 mol/L KOH.Besides,the multifunctional Ru NCs/Co₂P HMs exhibit good oxygen evolution reaction(OER) activity with an overpotential of 197 mV to reach the current density of 10 mA/cm² in 0.5 mol/L H₂SO₄,which is below that of the commercial RuO₂ electrocatalyst(248 mV).A two-electrode electrolyzer is assembled as well,in acid electrolyte,it achieves a current density of 10 mA/cm² at a voltage of 1.53 V,which is superior to that of the benchmark of precious metal-based electrolyzer(1.58 V).     

The preparation of ionic liquid based iron phosphate/CNTs composite via microwave radiation for hydrogen evolution reaction and oxygen evolution reaction

Water electrolysis is a promising method for hydrogen production, so the preparation of low-cost and efficient electrocatalysts with a quick and simple procedure is crucial. Herein, iron phosphate (Fe₇(PO₄)₆) was prepared via microwave radiation using ionic liquid (IL) as iron and phosphorus dual-source. This method is simple and rapid, and the product can be directly used as electrocatalysts without further treatment. The experimental results show that the IL can influence the morphology and electrocatalytic performance. Moreover, the addition of carbon nanotubes (CNTs) is favorable for formation of iron phosphate nanoparticles to improve the catalytic activities. As hydrogen evolution reaction (HER) catalyst, this iron phosphate/CNTs exhibits an onset overpotential of 120 mV, Tafel slope of 32.9 mV dec^-1, and current densities of 10 mA cm⁻² at overpotential of 185 mV. Then, it obtains a good activity for oxygen evolution reaction (OER) with a low onset potential of 1.48 V, Tafel slope of 73.3 mV dec^-1, and it only needs an overpotential of 300 mV to drive the 10 mA cm⁻². This bifunctional catalyst also shows good durability for HER and OER. This microwave-assisted method provides an outstanding strategy to prepare iron phosphate in a simple and fast process with good catalytic performance for water splitting.     

Monolayer 1T and 1T′ MoSO as Promising Electrocatalyst for Hydrogen Evolution based on First Principle Calculations

Molybdenum disulfide (MoS₂) has been regarded as one of the most promising candidates for replacing Pt group noble metals as an efficient electrocatalyst to enhance the hydrogen evolution reaction (HER) in consideration of its relatively high earth abundance. Recent studies show that the catalytic efficiency of MoS₂ for HER can be promoted by the presence of 1T-phase MoS₂. It is hard to precisely control the formation of 1T-MoS₂, however, due to its metastability relative to 2H-MoS₂. Elevating the stability of 1T phase allotrope is therefore of great importance and could be realized by replacing divalent S with monovalent elements or groups according to crystal field theory, which has been demonstrated through our first-principles density functional theory (DFT) calculation results. Differential Gibbs free energy analysis for hydrogen adsorption (ΔG_H*) suggest that 1T and 1T′ MoSO (O doped MoS₂) might be taken as potential candidate catalysts for HER process with better performance than 1T and 1T′ MoS₂. We also propose a probable approach to synthesize 1T and 1T′ MoSO under oxidation circumstance environment of graphene oxide.     

Phase‐Junction Electrocatalysts towards Enhanced Hydrogen Evolution Reaction in Alkaline Media

To ensure sustainable hydrogen production by water electrolysis, robust, earth‐abundant, and high‐efficient electrocatalysts are required. Constructing a hybrid system could lead to further improvement in electrocatalytic activity. Interface engineering in composite catalysts is thus critical to determine the performance, and the phase‐junction interface should improve the catalytic activity. Here, we show that nickel diphosphide phase junction (c‐NiP₂/m‐NiP₂) is an effective electrocatalyst for hydrogen production in alkaline media. The overpotential (at 10 mA cm^?2) for NiP₂‐650 (c/m) in alkaline media could be significantly reduced by 26 % and 96 % compared with c‐NiP₂ and m‐NiP₂, respectively. The enhancement of catalytic activity should be attributed to the strong water dissociation ability and the rearrangement of electrons around the phase junction, which markedly improved the Volmer step and benefited the reduction process of adsorbed protons.